Merge lane base check: develop 4c2a3e692a0f

Merge lane base check: run the full gate on `develop` at `4c2a3e692a0f2a83c08c3e1e8270cf3b373074bc` alone and report it certified or red: nothing had certified it since the last attempt. A red verdict files a fix task; it never holds the lane. Filed by the control plane (`app/merge_lane.py::_certify_idle`). How: run `python3 tools/merge_lane.py run` once. It takes this check's batch, gates that commit with the full gate in its sandbox and reports `certified` or `develop_red` itself. Never run the gate by hand: a hand-run green reports nothing, so no certificate is recorded.

develop 4c2a3e692a is red (lane reported develop_red). One test fails, also when rerun alone: test_virtual_nodes.py::test_a_regular_nodes_bootstrap_is_byte_identical_to_before_hosts_existed (golden digest mismatch). Likely culprit ffae502d10 (PR #7321, Task 11113). Memory: none applied.